The halachah allows us to cook on Yom Tov, but the question arises as to whether measuring is permissible as part of the process of food preparation. Chachamim forbade precise measuring on Yom Tov, but not making a “rough estimate,” of the measurements. Therefore, it would be forbidden to use a measuring cup to arrive at a precise amount. One may, however, use a measuring cup in order to roughly estimate an amount of rice. As long the intent is to arrive at a general estimate and not to measure a precise amount. It is permissible to use an ordinary glass that does not outline measurements to determine the amount of rice that one wishes to prepare.
Ha’Rav Ovadyah Yosef (a”h) states that measuring is permissible for the purpose of a mitzvah. Some people are accustomed to weighing matzah at the Seder to know precisely how much to eat. According to Rav Ovadiyah, these measurements are permissible on Yom Tov because they are made for the sake of a mitzvah.
